Leg 177 will core sediments in the southeast Atlantic sector of the Southern Ocean to study the
paleoceanographic history of the Antarctic region on short (millennial) to long (Cenozoic) time
scales. Six primary sites are located along a latitudinal transect across the Antarctic Circumpolar
Current (ACC) from 41° to 53°S, including two sites (TSO-6A/B, TSO-7C/B) within the circum
Antarctic siliceous belt. The sites are also arranged along a bathymetric transect ranging from 2100
to 4600-m water depths, intersecting all of the major deep- and bottom-water masses in the
Southern Ocean.

The general goals of Leg 177 are two-fold: (1) to augment the biostratigraphic, biogeographic, and
paleoceanographic history of the earlier Cenozoic, a period marked by the establishment of the
Antarctic cryosphere and the ACC; and (2) to target expanded sections of late Neogene sediments,
which can be used to resolve the timing of Southern Hemisphere climatic events on orbital and
suborbital time scales and which can be compared with similar records from other ocean basins and
with ice cores from Greenland and Antarctica. Drilling the proposed sites will provide the
sedimentary sequences needed to address a number of first-order objectives and questions in
southern high-latitude paleoclimatology and stratigraphy, including (1) the evolution of the ACC
and past changes in the position of the Polar Front Zone and the Antarctic sea-ice field; (2) the
evolutionary history and stability of the Antarctic cryosphere; (3) changes in Southern Ocean
productivity, nutrient cycling, and pCO2 and their role in global biogeochemical
cycles and climate evolution; (4) changes in the mixing ratio of various deep- and bottom-water
masses in the Antarctic (e.g., North Atlantic Deep Water); (5) the response of the Southern Ocean
to orbital forcing and the phase relationships to climatic changes in low and northern high latitudes;
(6) documentation of abrupt climate change on millennial time scales in the Southern Ocean and
their correlation with ice and sediment core records from other areas; and (7) recovery of the first
continuous sequences from the circum-Antarctic siliceous belt that will provide insight into early
low-temperature chert diagenesis.